February 2008 - Boost-users

gzip_compressor cannot be flushed and closed properly
by Mengda Wu 27 Feb '08

27 Feb '08

Hi, I have a code block trying to output a series of gzip files. I wish to have all the files flushed after the block. But the files can only be flushed after exiting the whole program. The files still have zero size after I try to close them. I am using std::vector to store all the pointers to boost filtering_ostream. Can you help? //Open iostreams char filename[20]; std::vector<boost::iostreams::filtering_ostream *> os_vector; for(i=0; i<4; i++) { sprintf(filename, "file_%d.gz", i ); std::ofstream *of = new std::ofstream(filename, std::ios_base::binary); boost::iostreams::filtering_ostream* os = new boost::iostreams::filtering_ostream; os->push(boost::iostreams::gzip_compressor()); os->push(*of); os_vector->push_back(os); } //Output something for(i=0; i<4; i++) { boost::iostreams::filtering_ostream* os = os_vector[i]; os<<"Output something here" << std::endl; } //Close streams for(i=0; i<4; i++) { boost::iostreams::filtering_ostream* os = os_vector[i]; os->strict_sync(); os->pop(); os->reset(); } Thanks, Mengda

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[interprocess] Many-to-many communication
by Boris 27 Feb '08

27 Feb '08

I have an application which needs to communicate with several other applications on the same machine. I thought to use message queues but quickly ran into a problem: Either I create as many threads as there are message queues which all block and wait for incoming data or I constantly poll all message queues. The later should be easily possible with try_receive(). However it doesn't sound like a good idea to poll continuously? And I assume integrating the message queue somehow into Boost.Asio is not something easily possible? Thus for many-to-many communication shared memory is probably the way to go? Boris

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BGL: Bug in depth_first_search
by Christian Sturz 27 Feb '08

27 Feb '08

Hi, as it seems I've found a bug in the depth_first_search algorithm. I want to use it with my own ColorMap and a start vertex. Here is the code taken from http://www.boost.org/libs/graph/example/dfs-example.cpp with some slight modifications: ------------------------------------ include <boost/graph/adjacency_list.hpp> #include <boost/graph/depth_first_search.hpp> #include <boost/pending/integer_range.hpp> #include <boost/pending/indirect_cmp.hpp> #include <iostream> using namespace boost; template < typename TimeMap > class dfs_time_visitor:public default_dfs_visitor { typedef typename property_traits < TimeMap >::value_type T; public: dfs_time_visitor(TimeMap dmap, TimeMap fmap, T & t) : m_dtimemap(dmap), m_ftimemap(fmap), m_time(t) { } template < typename Vertex, typename Graph > void discover_vertex(Vertex u, const Graph & g) const { put(m_dtimemap, u, m_time++); } template < typename Vertex, typename Graph > void finish_vertex(Vertex u, const Graph & g) const { put(m_ftimemap, u, m_time++); } TimeMap m_dtimemap; TimeMap m_ftimemap; T & m_time; }; int main() { // Select the graph type we wish to use typedef adjacency_list < vecS, vecS, directedS > graph_t; typedef graph_traits < graph_t >::vertices_size_type size_type; // Set up the vertex names enum { u, v, w, x, y, z, N }; char name[] = { 'u', 'v', 'w', 'x', 'y', 'z' }; // Specify the edges in the graph typedef std::pair < int, int >E; E edge_array[] = { E(u, v), E(u, x), E(x, v), E(y, x), E(v, y), E(w, y), E(w, z), E(z, z) }; #if defined(BOOST_MSVC) && BOOST_MSVC <= 1300 graph_t g(N); for (std::size_t j = 0; j < sizeof(edge_array) / sizeof(E); ++j) add_edge(edge_array[j].first, edge_array[j].second, g); #else graph_t g(edge_array, edge_array + sizeof(edge_array) / sizeof(E), N); #endif // Typedefs typedef boost::graph_traits < graph_t >::vertex_descriptor Vertex; Vertex root = source( edge_array[2],g ); typedef size_type* Iiter; // discover time and finish time properties std::vector < size_type > dtime(num_vertices(g)); std::vector < size_type > ftime(num_vertices(g)); size_type t = 0; dfs_time_visitor < size_type * >vis(&dtime[0], &ftime[0], t); std::vector<default_color_type> color(num_vertices( g ) ); depth_first_search(g, visitor(vis), &color[0], root ); return 0; } ------------------------------------ So, I've added a ColorMap and a start vertex as 3. and 4. argument to "depth_first_search". This code can't be compiled with the gcc on a Debian Etch machine. These are the compiler errors: dfs.cc: In function `int main()': dfs.cc:47: warning: unused variable 'name' /usr/include/boost/graph/depth_first_search.hpp: In function `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]': dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:197: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'initialize_vertex' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:200: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'start_vertex' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:207: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'start_vertex' /usr/include/boost/graph/depth_first_search.hpp: In function `void boost::detail::depth_first_visit_impl(const IncidenceGraph&, typename boost::graph_traits<G>::vertex_descriptor, DFSVisitor&, ColorMap, TerminatorFunc) [with IncidenceGraph = boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, boost::no_property, boost::no_property, boost::no_property, boost::listS>, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*, TerminatorFunc = boost::detail::nontruth2]': /usr/include/boost/graph/depth_first_search.hpp:201: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:103: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'discover_vertex' /usr/include/boost/graph/depth_first_search.hpp:201: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:120: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'examine_edge' /usr/include/boost/graph/depth_first_search.hpp:201: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:123: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'tree_edge' /usr/include/boost/graph/depth_first_search.hpp:201: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:127: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'discover_vertex' /usr/include/boost/graph/depth_first_search.hpp:201: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:133: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'back_edge' /usr/include/boost/graph/depth_first_search.hpp:201: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:136: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'forward_or_cross_edge' /usr/include/boost/graph/depth_first_search.hpp:201: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:141: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'finish_vertex' /usr/include/boost/graph/depth_first_search.hpp: In member function `void boost::DFSVisitorConcept<Visitor, Graph>::constraints() [with Visitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, Graph = main()::graph_t]': /usr/include/boost/concept_check.hpp:48: instantiated from `void boost::function_requires(boost::mpl::identity<T>*) [with Concept = boost::DFSVisitorConcept<boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, main()::graph_t>]' /usr/include/boost/graph/depth_first_search.hpp:191: instantiated from `void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = main()::graph_t, DFSVisitor = boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>, ColorMap = boost::default_color_type*]' dfs.cc:76: instantiated from here /usr/include/boost/graph/depth_first_search.hpp:36: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'initialize_vertex' /usr/include/boost/graph/depth_first_search.hpp:37: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'start_vertex' /usr/include/boost/graph/depth_first_search.hpp:38: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'discover_vertex' /usr/include/boost/graph/depth_first_search.hpp:39: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'examine_edge' /usr/include/boost/graph/depth_first_search.hpp:40: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'tree_edge' /usr/include/boost/graph/depth_first_search.hpp:41: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'back_edge' /usr/include/boost/graph/depth_first_search.hpp:42: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'forward_or_cross_edge' /usr/include/boost/graph/depth_first_search.hpp:43: error: 'struct boost::bgl_named_params<dfs_time_visitor<main::size_type*>, boost::graph_visitor_t, boost::no_property>' has no member named 'finish_vertex' So, there seem to be a bug in the algorithm. When calling it as defined in the exampl file from the Boost side without a ColorMap and a vertex, it works fine. Could you verify this and tell me if you can reproduce it? Thank you. Regards, Christian -- GMX startet ShortView.de. Hier findest Du Leute mit Deinen Interessen! Jetzt dabei sein: http://www.shortview.de/?mc=sv_ext_mf@gmx

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[serialization] class template with virtual base
by Richard Crossley 27 Feb '08

27 Feb '08

Hi, I've been searching the archives but am not finding an answer... Is there any way to serialise D<> via a pointer to its base B when the types used to parameterise D<> are not known in advance? i.e. How do I register D<> with the serialisation library? For Example... struct B{ virtual void fn() =0; }; template<typename T> struct D : B{ virtual void fn(){}; }; B* b = new D<char>(); .... anArchive & b; Thanks, Richard.

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Re: [Boost-users] boost::crc32 - visual studio crt - bug?!
by gfsdgadas＠Safe-mail.net 27 Feb '08

27 Feb '08

I do not like the idea of changing my compile flags (I really do like that option for my debug builds!) just because of boost crc32. What about changing the header the request way, marking all casts using &0xFF? I do not see any reason for those safe marks not being introduces into boost crc.

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Boost PP lib
by Hicham Mouline 27 Feb '08

27 Feb '08

hi, in an ealier post, i was helped to write explicit template instantiations as: #define FINH1 (EC)(EP)(AC)(AP) #define FINH2 (C)(D)(E)(F)(G) #define FINH3 (2)(3) #define M(r, product) template class Tree<BOOST_PP_SEQ_ENUM(product)>; BOOST_PP_SEQ_FOR_EACH_PRODUCT(M, (FINH1)(FINH2)(FINH3)) That nicely generated: template class Tree<EC,C,2>; template class Tree<EC,C,3>; template class Tree<EC,D,2>; template class Tree<EC,D,3>; ... what i need now is coupling FINH2 and FINH3 (i don't want their crossproduct) as in: #define FINH1 (EC)(EP)(AC)(AP) #define FINH2 (C,2)(D,2)(E,3)(F,3)(G,3) #define M(r, product) template class Tree<BOOST_PP_SEQ_ENUM(product)>; BOOST_PP_SEQ_FOR_EACH_PRODUCT(M, (FINH1)(FINH2)) But that does't work because the commas in FINH2 are taken as macro arguments which fails... ideas are appreciated... regards,

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Boost Interprocess docs
by Wolfram Stering 27 Feb '08

27 Feb '08

Hello List, if I wanted to read Boost.Interprocess documentation, where would I look for it? I want to evaluate Boost.Interprocess for use in a setuid application with requires a GUI part using a backend (setuid) and a frontend (gui) process. Boost.Interprocess is scheduled to be included in release 1.35, if I remember correctly. thanks for your help, best regards, -wolfi -- Wolfram Stering (Entwicklung) HALE electronic GmbH Eugen-Müller-Straße 18, 5020 Salzburg, Austria Tel: +43 (662) 439011 550 Fax: +43 (662) 439011 9 http://www.hale.at/ Firmenbuchnummer: FN 66801m HG Salzburg -- Scanned by MailScanner.

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circular_buffer iterator problem
by abir basak 27 Feb '08

27 Feb '08

Hi, I have a boost svn trunk checkout (latest one). It seems boost circular_buffer has a iterator problem for converting from non const to const iterator, on visual studio 7.1 (2003) release build only. Can someone check for it ? (It used to work on boost 1.34) for eg, using namespace boost::assign; typedef boost::circular_buffer<int> CB; std::vector<int> v; v+=1,2,3,4,5,6,7,8,9,10,11,12; CB buf(10,v.begin(),v.end()); CB::iterator it = buf.begin(); CB::const_iterator it1 = buf.begin();/// This line doesn't compile on release build only. a second (and little different) question, why boost::assign doesn't work with circular_buffer directly which has 2 iterator construct like most other STL containers ? thanks abir -- Abir Basak, Member IEEE Software Engineer, Read Ink Technologies B. Tech, IIT Kharagpur email: abir(a)abirbasak.com homepage: www.abirbasak.com

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boost::lambda::bind internal object storage
by Zian Smith 27 Feb '08

27 Feb '08

Hello, Can someone explain why I see 5 constructor calls here, but only 4 destructor calls? Is the bind function neglecting to destroy one of the internal copies made or am I missing something? I understand that if I use the "var" function, the problem is eliminated, but I'd still like to figure this out. I'm using boost 1.33.1 -Thanks! //================================= #include <iostream> #include <vector> #include <algorithm> #include "boost/lambda/bind.hpp" using namespace std; using namespace boost::lambda; struct woot { woot() { cout << "woot constr\n"; } woot(const woot& o) { cout << "woot copy-constr\n"; } ~woot() { cout << "woot destr\n"; } }; void do_nothing(const woot& w) { } int main() { woot w; vector<char> v; for_each(v.begin(), v.end(), bind(do_nothing, w)); } //================================= Output: ------- woot constr woot copy-constr woot copy-constr woot copy-constr woot destr woot destr woot copy-constr woot destr woot destr ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs

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ASIO ssl::stream read/write_some question.
by Derrick Hathaway 27 Feb '08

27 Feb '08

Could someone please shed some light on ASIO SSL reads and writes for me? The names of the read and write functions for the ssl::stream (read_some and write_some) imply to me that the buffer(s) may not be completely filled/sent with a read/write. Do I need to have some intermediate handler that will begin another async_read/write_some until my buffer is filled/flushed? The documentation doesn't seem to indicate that this is necessary. It makes sense from the example that the reads may not fill the provided buffer before invoking the handler. So it may be necessary to call read_some multiple times until the expected number of bytes is received. But is this also the case with writes, and if so, how do I manage multiple writes if I provide a vector of buffers to be written with and async_write_some? Thanks in advance. Derrick

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